• Erik Farin, Michaela Nagl, Lukas Gramm, Katja Heyduck, and Manuela Glattacker.
• Department of Quality Management and Social Medicine, University Medical Center Freiburg, Engelbergerstr. 21, 79106, Freiburg, Germany, erik.farin@uniklinik-freiburg.de.
• Qual Life Res. 2014 May 1;23(4):1255-65.

ObjectiveStudy aim was to translate the PROMIS(®) pain interference (PI) item bank (41 items) into German, test its psychometric properties in patients with chronic low back pain and develop static subforms.MethodsWe surveyed N = 262 patients undergoing rehabilitation who were asked to fill out questionnaires at the beginning and 2 weeks after the end of rehabilitation, applying the Oswestry Disability Index (ODI) and Pain Disability Index (PDI) in addition to the PROMIS(®) PI items. For psychometric testing, a 1-parameter item response theory (IRT) model was used. Exploratory and confirmatory factor analyses as well as reliability and construct validity analyses were conducted.ResultsThe assumptions regarding IRT scaling of the translated PROMIS(®) PI item bank as a whole were not confirmed. However, we succeeded in devising three static subforms (PI-G scales: PI mental 13 items, PI functional 11 items, PI physical 4 items), revealing good psychometric properties.ConclusionThe PI-G scales in their static form can be recommended for use in German-speaking countries. Their strengths versus the ODI and PDI are that pain interference is assessed in a differentiated manner and that several psychometric values are somewhat better than those associated with the ODI and PDI (distribution properties, IRT model fit, reliability). To develop an IRT-scaled item bank of the German translations of the PROMIS(®) PI items, it would be useful to have additional studies (e.g., with larger sample sizes and using a 2-parameter IRT model).

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